Today, there is a rapid increase in the building of new mobile telecommunication networks, such as GSM (Global System for Mobile communication) networks.
A cellular mobile network typically includes a plurality of base stations being connected together by means of switching nodes such as a Base Station Controller (BSC) and/or a Mobile Switching Centre (MSC). Each base station provides radio coverage over an area known as a cell, for radio communication with mobile phones located therein. Each of the base stations and the mobile phones include, among other things, a transceiver for radio communication over radio frequency channels. Each mobile network is allocated by licence a certain limited radio frequency band spectrum for transmissions, and efforts are made by network operators to provide the greatest possible traffic capacity within the allocated frequency band. In other words, the operators attempt to maximise the number of possible ongoing call connections within the limits of the available radio channels.
Mobile networks are built and operated by different operators who have been awarded a licence for a particular frequency band. However, the different frequency bands allocated to the operators are a limited resource for which a licence may be very costly to obtain, at least in some countries.
As mentioned above, operators of mobile networks are usually faced with the problem of how to utilise their frequency band in the most efficient way once the licence has been obtained. Furthermore, some of the operators also own and control a fixed telecommunication network.
When communicating over a fixed network, unlicensed cordless radio technology may be used for so-called cordless phones. A Home Base Station (HBS) is then connected to a fixed line of the fixed network for providing a cordless radio interface between the fixed line and the cordless phone. The cordless phone may be used in a limited area of radio coverage from the HBS using a suitable short distance radio interface, such as Bluetooth, DECT or CT2. Both the HBS and the cordless phone include a transceiver for radio communication over a particular frequency band for which no licence is required.
An operator operating both a fixed network and a mobile network would benefit if more telecommunication traffic is transmitted via the fixed network instead of over the mobile network. By reducing the traffic in the mobile network, it would be possible to use larger cells in the mobile network without having traffic congestion in the cells. This is of particular interest in dense areas such as cities. The cost for network infrastructure is thereby reduced and cell planning is facilitated for the operator.
Using only one mobile terminal for communication over both the fixed and the mobile network, having a single telephone number, would be a great benefit for subscribers. Moreover, if the fixed network can be used in preference to the mobile network, the cost for making calls can also be reduced for subscribers. Further, it would be highly desirable for operators to be able to offer an attractive combined subscription for both mobile and fixed telecommunication to subscribers, involving unified charging among other things.
However, there is a problem to correctly route an incoming call to such a combined mobile terminal over either the fixed network or the mobile network when a single telephone number is used.